1. Scope of Invention
This invention relates generally to apparatus for cutting and forming sheet metal, and more particularly to an accessory holddown bar for use in conjunction with a power corner notcher.
2. Prior Art
Power corner notchers, more generally referred to as power notchers, are well known in the industry. Applicant distributes a line of such hydraulic power notchers manufactured by Boschert GmbH+Co. KG, in Lorrach, Germany under the trademark EAGLE. These power notchers are designed to form a 90.degree. notch into an edge of a piece of sheet metal which may range in thickness up to in the range of thickness of about 1/4".
These power notchers include a horizontal table which defines a work surface having slots formed therein for receiving easily engagable clamps which secure, for example, an elongated bar stop having orthogonally oriented side edge surfaces against which the sheet metal may be abutted and aligned for proper positioning prior to the notching operation. These adjustable clamps may be positionable as desired atop the table and within the slots formed therein. Further adjustment is achieved by these adjustable clamps by rotation about an upright central axis thereof so as to angularly position these stop bars with respect to the cutting blades of the power notcher. Further adjustment is achieved by the slidable positioning of the stop bar with respect to the adjustable clamps before tightening thereof.
In notching sheet metal of this thickness and strength, the edges of the sheet metal adjacent to the notched area tend to buckle or deform upwardly in an undesirable fashion. An accessory for the Boschert equipment for addressing this problem is available in the form of spring actuated holddowns which are attached to the movable cutting head or ram of the power notcher immediately adjacent to the cutting blades so as to engage against the upper surface of the sheet metal as the movable cutting head is downwardly displaced during each cutting operation. However, in addition to being relatively expensive, these holddowns are somewhat less than effective in eliminating this edge distortion during notching.
The present invention is an improvement in the stop bar so as to expand its general useful characteristics into a combination stop bar and holddown device for preventing edge distortion of the sheet metal completely. The improvement represents the addition of an inside square corner-shaped recess formed into the lower surface of the stop bar along one side edge thereof. By this arrangement, a recessed upright abutting surface is provided against which the sheet metal may be aligned and held, and a horizontal holddown surface displaced above the working surface a distance or height generally equal to the thickness of the sheet metal being cut. The improved combination stop bar and holddown bar also includes a viewing hole to ensure that the sheet metal is fully against the recessed abutting surface prior to notching operation for optimal positional accuracy of the sheet metal.